copy method
Implementation
@override
SpotLight copy(Object3D source, [bool? recursive]) {
super.copy(source);
SpotLight source1 = source as SpotLight;
distance = source1.distance;
angle = source1.angle;
penumbra = source1.penumbra;
decay = source1.decay;
target = source1.target!.clone();
shadow = source1.shadow!.clone();
return this;
}